Machines used for cold forming hexagonal heads on the ends of steel bolts are in widespread use. Typical machines form the bolts from a coil of steel wire which has the desired diameter necessary to form the shank of the bolt. The wire is fed through an opening in one part of the machine, to extend into a head-forming cavity. The internal configuration of the head-forming cavity is in the form of the proper dimensions of the head (usually a hex head) to be formed on the end of the bolt.
The opposite end of the cavity from the one into which the wire is fed has a movable knock-out pin in it. This knock-out pin is driven by a ram into the cavity to compress the wire to form the head on the end of the bolt. The knock-out pin has a pad on the end, which typically is in the form of a flat circular platform, having a diameter less than the smallest cross-sectional transverse diameter of the knock-out pin. This pad squeezes some of the metal at the top of the bolt hex head into the corners to ensure proper forming at the edges, which ultimately become edges at the top of the bolt. After the bolt is formed, the machine is opened; and the knock-out pin continues to move into the cavity to drive the bolt from the cavity. The knock-out pin and ram then are withdrawn to the original position, and the cycle is repeated.
Even in the manufacture of relatively small diameter bolts, tremendous forces are applied to the knock-out pin during the formation of the bolts when the press comes together to form the head on the end of the bolt. These forces are in the form of a hammer-like shock, and place significant stress on the knock-out pin. The initial shock is applied to the flat circular pad on the end of the knock-out pin. Operation of a typical bolt making machine generally results in frequent fracture type failures of the knock-out pins, which then must be replaced. During the times that the knock-out pins are being replaced in the machine, the machine cannot be operated for its intended function. Consequently, the "down time" during which a machine is unable to be operated for replacement of the knock-out pins has a significant impact on the productivity of the machine.
It is desirable to provide a knock-out pin for a cold forming steel bolt making machine which has increased life over presently known knock-out pins.